Potentiometric Titration

1. Potentiometric Titration
Principal
Potentiometric Titration (electrometric method)
Potentiometric titration is a method of chemical analysis. This technqiue relies on the measurement of electromotive force
(EMF) of a solution using a set of indicator and reference electrodes. The potential or EMF of a solution depends on the
nature and concentration of the ions of the test substance.
The EMF or potential is measured in millivolts (mV) using a potentiometer having an indicator and reference electrode.

5. Potentiometric Titration Method
Potentiometric Titration is done via the usage of two electrodes – an indicator electrode and a reference electrode
(generally a hydrogen electrode or a silver chloride electrode). One half-cell is formed with the indicator electrode and
the ions of the analyte, which is generally an electrolyte solution. The other half-cell is formed by the reference
electrode.
The overall cell potential can be calculated using the formula given below.
Ecell=Eind–Eref+Esol (salt bridge-KCl)
Where the potential drop between the indicator and reference electrodes over the electrolyte solution is given by Esol.
The overall cell potential, Ecell is calculated in every interval where the titrant is measured and added. Now, a graph is
plotted with the Potential difference on the Y-axis and the volume on the X-axis as shown below.

75. Types of Potentiometric Titration
There are four types of titration that fall under the category of potentiometric titration, namely acid-base titration, redox
titration, complexometric titration, and precipitation titration.
Acid-Base Titration: This type of potentiometric titration is used to determine the concentration of a given acid/base by
neutralizing it exactly using a standard solution of base/acid whose concentration is known.
Redox Titration: This type of potentiometric titration involves an analyte and titrant that undergo a redox reaction. An
example of this type of titration would be the treatment of an iodine solution with a reducing agent which produces iodide
ion (a starch indicator is used to get the endpoint).
Complexometric Titration: This type of titration can also be referred to as chelatometry. In this method, a coloured
complex is formed, indicating the end point of the titration. This method is used to determine a mixture of metal ions in a
given solution.
Precipitation Titration: This type of titration involves a reaction between the given analyte and the titrant wherein an
insoluble precipitate is formed. The end-point of this titration is noted when the addition of the titrant no longer forms a
precipitate.